1875.] 



Replacement of Metals in a Voltaic Cell. 



49 



We conceive that the explanation of this reaction is that the po- 

 tassium chloride in solution is itself electrolyzed. The occurrence of hydro- 

 gen against the platinum plate might be ascribed to the electrolysis of the 

 water, the resistance of which was diminished by the dissolved salt ; but 

 this alone in no way accounts for the simultaneous formation of free alkali. 

 If any objector should contend that the nascent hydrogen had decomposed 

 chloride of potassium, that would still leave the removal of the acid un- 

 explained ; and as the liberated potassium would instantly decompose an 

 equivalent of water, we should have a chemical reaction resulting in nothing 

 but the restoration of the original state of things, 



H + KC1 + H 2 = HC1 + KH0 + H = KC1 + H 3 + H. 



It might be supposed that the force produced by the contact of the two 

 metals would expend itself upon the decomposition of a small amount of po- 

 tassium salt, and that then the action would cease. But experiment shows 

 the action just described to be continuous. Several determinations were 

 made of the alkali in the divided-cell experiment described above, at 30 

 minutes' and at 60 minutes' duration. The results were far from uniform ; 

 but on the average the double period showed an increase of 70 per cent. 

 Better observations were obtained when the hydrogen evolved was taken as 

 the measure of the action. The wire connecting the strips of magnesium 

 and platinum was caused to pass through the whole length of a graduated 

 tube, which was filled with the solution and inverted in it as in the annexed 

 diagram. Hydrogen was evolved at once, and a certain volume was col- 



VOL. XXIV. 



